Process for fabricating stiction control bumps on optical membrane via conformal coating of etch holes

Abstract

An electrostatically driven optical membrane comprises a support structure and a membrane structure separated from the support structure by an electrostatic cavity. Stiction plugs are formed in the membrane structure. The plugs extend from a surface of the membrane. In one implementation, the plugs are hollow to allow a subsequent release process in which the sacrificial layer is removed.

What is claimed is:  
     
       1. A process for fabricating stiction features on an electrostatically driven optical membrane, the process comprising: 
       forming holes in a membrane material layer;  
       performing a partial etch of a sacrificial layer under the membrane after forming the holes to thereby form depressed regions in the sacrificial layer; and  
       performing a deposition through the holes and into the depressed regions to form elevated regions around the holes relative to a surface of the membrane to thereby reduce a risk of stiction adhesion of the membrane to an opposed surface across an electrostatic cavity.  
     
     
       2. A process as claimed in  claim 1 , wherein step of forming the holes in the membrane material layer comprises forming the holes completely through the membrane material layer. 
     
     
       3. A process as claimed in  claim 1 , further comprising releasing the membrane by removing a sacrificial layer from underneath the membrane material layer. 
     
     
       4. A process as claimed in  claim 1 , further comprising performing a membrane release process by allowing an etchant to attack a sacrificial layer under the membrane through the holes. 
     
     
       5. A process as claimed in  claim 1 , further comprising performing a membrane release process by allowing hydrofluoric acid to attack a sacrificial layer under the membrane through the holes. 
     
     
       6. A process as claimed in  claim 1 , further comprising performing a membrane release process by allowing an etchant to attack a sacrificial layer under the membrane through the holes after a step of coating the holes. 
     
     
       7. A process for fabricating a membrane for an optical filter device having stiction control features, the process comprising 
       providing support material;  
       forming a sacrificial layer on the support material;  
       providing a membrane layer on the sacrificial layer;  
       patterning the membrane layer to form a membrane structure including forming holes in the membrane layer and tethers between a body portion of the membrane structure and an outer portion of the membrane structure;  
       coating the holes to form elevated regions around the holes; and  
       removing at least part of the sacrificial layer to release the membrane structure.  
     
     
       8. A process as claimed in  claim 7 , wherein sacrificial layer is silicon oxide. 
     
     
       9. A process as claimed in  claim 7 , wherein the membrane layer is a wafer material is that is bonded to the sacrificial layer. 
     
     
       10. A process as claimed in  claim 7 , further comprising etching an optical port from a backside of the support material to a depth of the sacrificial layer. 
     
     
       11. A process as claimed in  claim 7 , wherein the support material is a semiconductor wafer. 
     
     
       12. A process as claimed in  claim 7 , wherein step of forming the holes in the membrane material layer comprises forming the holes completely through the membrane material layer. 
     
     
       13. A process as claimed in  claim 7 , wherein the step of removing the sacrificial layer comprises etching the sacrificial layer under the membrane through the coated holes. 
     
     
       14. A process as claimed in  claim 7 , wherein the step of removing the sacrificial layer comprises etching the sacrificial layer under the membrane through the coated holes with hydrofluoric acid. 
     
     
       15. A process as claimed in  claim 7 , wherein step of coating the holes comprises a conformal deposition process. 
     
     
       16. A process as claimed in  claim 7 , wherein step of coating the holes comprises a conformal polysilicon deposition process. 
     
     
       17. A process for fabricating a membrane for an optical filter device having stiction control features, the process comprising 
       providing support material;  
       forming a sacrificial layer on the support material;  
       providing a membrane layer on the sacrificial layer;  
       patterning the membrane layer to form a membrane structure including forming holes in membrane layer;  
       performing a partial etch of the sacrificial layer under the membrane structure after the step of forming the holes to thereby form depressed regions in the sacrificial layer;  
       performing a deposition through the holes and into the depressed regions to form elevated regions around the holes; and  
       removing at least part of the sacrificial layer to release the membrane structure.  
     
     
       18. An electrostatically driven optical membrane, comprising: 
       a support structure  
       a membrane structure separated from the support structure by an electrostatic cavity; and  
       stiction plugs that are located in holes in the membrane structure.  
     
     
       19. An electrostatically driven optical membrane as claimed in  claim 18 , wherein the stiction plugs extend from a surface of the membrane structure. 
     
     
       20. An electrostatically driven optical membrane as claimed in  claim 18 , wherein the stiction plugs comprise polysilicon. 
     
     
       21. An electrostatically driven optical membrane as claimed in  claim 18 , wherein the stiction plugs are deposited in a conformal deposition process. 
     
     
       22. An electrostatically driven optical membrane as claimed in  claim 18 , wherein the stiction plugs are conductive. 
     
     
       23. An electrostatically driven optical membrane as claimed in  claim 18 , wherein the stiction plugs are insulative. 
     
     
       24. An electrostatically driven optical membrane, comprising: 
       a support structure  
       a membrane structure separated from the support structure by an electrostatic cavity; and  
       stiction plugs in the membrane structure; wherein the stiction plugs are hollow.  
     
     
       25. An electrostatically driven optical membrane, comprising: 
       a support structure  
       a membrane structure separated from the support structure by an electrostatic cavity; and  
       multiple stiction plugs in the membrane structure, which are arranged around an optical axis of the membrane structure; wherein the stiction plugs extend through holes from an upper surface of the membrane structure into the electrostatic cavity in a direction of the support structure.